Introduction to Python Day 2

Verjinia Metodieva and Daniel Parthier

2025-02-04

Jupyter Notebook

Recap homework

Let’s take a look at the homework

Functions part 2

Goal of today

import numpy as np
import os

def AP_check(folder):
    AP_sweep_count = 0
    for filename in os.listdir(folder):
        if filename.endswith('.csv'):
            with open(os.path.join(folder, filename), 'r') as file:
                data = np.loadtxt(file, skiprows=1)
                if any(data > 20):
                    AP_sweep_count += 1
                    print("AP found in " + filename)
                else:
                    print('No AP in ' + filename)
    return AP_sweep_count

file_path = 'data/sweeps_csv/'
sweep_count = AP_check(file_path)
print(sweep_count)

Global vs. Local

  • Scopes
  • Local variables live and die inside a function
  • Global variables
    • declared outside of functions
    • lost when programm closed

Short interlude

  • Whole numbers: Integers int
type(1)
int
number_string = "1"
number = int(number_string)
print(number)
type(number)
1
int
  • Real numbers: Floats float
type(1.0)
float
fake_integer = float(1)
type(fake_integer)
float
  • Most of the time it might not matter1
1 == 1.0
True
  • Sometimes there is a difference, and we will see later why

But sometimes it does

  • Sometimes you will see is instead of ==.
1 == 1.0
1 is 1.0
True
False
  • They often do the same thing but work differently
    • Careful when using it!
    • is and is not is also checking the type!

Conditional statements

The important question of what to do “if” something happens.

  • Programming languages are languages
  • if something is True
    • you should do something
  • else
    • do something else
if *statement*:
    print("the *statement* is true")
else:
    print("the *statement* is false")

Multiple if-statements

value = 3
1if value == 1:
    print("the value is 1")
2elif value == 2:
    print("the value is 2")
3elif value == 3:
4    print("the value is 3")
else:
    print("the value is something else")
1
Check if value is 1
2
Check if value is 2
3
Check if value is 3
4
Execute block 
the value is 3

Short forms for conditionals

amplitude = 24
is_action_potential = "is AP" if amplitude > 0 else "no AP"
print(is_action_potential)
is AP
  • You can write a lot on one line
    • Do if you have to but be careful

How to check if everything is true?

  • Validate all the statements in a list
everything_is_true = [True, True, True]
something_is_true = [True, False, False]

all(everything_is_true)
all(something_is_true)
True
False
  • Sometimes only something has to be true
any(everything_is_true)
any(something_is_true)
True
True

For loops

for *element* in *iterable*:
    *body*
  • iteration is the repetition of a process until a specific condition is met
  • what’s iterable?
# calcualte a sum
list_to_sum = [2,3,4,5,7]
num_sum = 0
for val in list_to_sum:
   num_sum = num_sum + val

TO DO

Given:
A = [3, 4, 5, 9, 12, 87, -65, 300, 450, -32]

Use for loops to:
1. Add 3 to each element of the list
2. Calculate the average of the list, but negative values are calculated as 0s
3. Find the maximum value
4. Find the index (position) of the max value